Display screen or portion thereof with a graphical user interface



FIG. 1 is a front view of a display screen or portion thereof with a graphical user interface, showing our new design, according to a first embodiment thereof.

FIG. 2 is a front view of a display screen or portion thereof with a graphical user interface, showing our new design, according to a second embodiment thereof.

FIG. 3 is a front view of a display screen or portion thereof with a graphical user interface, showing our new design, according to a third embodiment thereof.

FIG. 4 is a front view of a display screen or portion thereof with a graphical user interface, showing our new design, according to a fourth embodiment thereof; and,

FIG. 5 is a front view of a display screen or portion thereof with a graphical user interface, showing our new design, according to a fifth embodiment thereof.

The broken lines illustrate the display screen or portion thereof and form no part of the claimed design. 

CLAIM The ornamental design for a display screen or portion thereof with a graphical user interface, as shown and described. 